I've gone through a bit of the code in the demo of Arms Devicer and can give requirement for many of the scenes for Rio. I don't know anything else about the other characters, though, so if anyone can fill that in, it'd be great help. I can only read a little Japanese, so it's a bit difficult looking through these things.
Inn/Pub
Resting when aroused or with 100+ Lust (first stat shown in the main menu) gives you the choice to Sleep (Top), Masturbate (Middle), or Walk around town (Bottom) when you wake up.
Masturbation - 3 Scenes in total
Walk around town - Head to the Pub
At the Pub, talk to the man with the bandanna at the bottom left table to have a coin toss betting game.
Win --> 300 G
Lose (Lust <= 30) - Run away after losing once
Lose (Lust <= 50) - Run away after losing twice
Lose (Lust <= 100) - Run away after losing three times
Lose (Lust > 100) - Continue Coin Toss after removing all 3 articles of clothing
Win - 1000 G
Lose - Masturbate
The next day, if you go back to the bar at night and talk to the guy, you will get an additional scene.
Mission 1: Clear out the Slums
Head east in the city to reach the slums.
Groups of enemies (2 enemies, but 1 target)can sexually harass you during battle. They can grope Rio's breasts, crotch, do fellatio, or just fuck her.
Losing in the Slums gives a number of scenes. To get the next scene, you must see the scene prior (i.e., Lust > 100 scene requires Lust < 100 Scene)
Lust < 100 - Sex, Hate
Lust < 200 - Gang Rape, Dislike
Lust < 300 - Gang Rape, Turning
Lust < 400 - Gang Rape, Like
Lust < 500 - Gang Rape, Love, Pregnant
Lust > 500 - Gang Rape, Slave (The game is supposed to revert to before this scene, but it causes a few problems. Battles may or may not work, since the appropriate image is not included. The level will be reset to 1 and Rio will have a collar and chain)
Mission 2: Defeat the Monster in the Forest.
Losing in the Forests to the north of the city gives a number of scene. They are sequential. The scenes are of a Bestiality nature.
Lust < 100 - Sex, Hate
Lust < 200 - Sex, Turning
Lust < 300 - Sex, Like
Lust < 500 - Sex, Love, There is an extra scene where the man who rescues Rio rapes her
Lust > 500 - Sex, Love, Choice of Escaping (continue) or Submitting (Game Over)
Mission 3: Clean out the Marshes
Losing in the Mashes to the northeast of the city gives sequential scenes with a tentacle theme
Lust < 100 - Sex, Dislike
Lust < 300 - Sex, Like
Lust > 300 - Sex, Love
After these scenes (I believe), every time you lose, you will be impregnated by the tentacles; however, the game crashes with any battle, since the image is not included. There is also a game over, but I can't figure it out.
Mission 4: Investigate the Castle
There is nothing specific at this castle
Gale Scenes
Gale is available for Mission 4. He's the black man standing to the east of the Guild, and you can hire him for 300 G. The scenes focus on NTR.
Lose Battle (may need to be in castle) - Rape, Dislike
Lust > 100 - Sex, Submissive
Lust > 200 - Sex, Hiding from Mite (Male who can join your party)
Lust > 300 - Vibrator in front of Mite
Lust > 400 - Sex with Mite (not satisfied) and Sex with Gale, Sex with people in town
Nilz Scene
Nilz is available at the same time as Gale. He is in the small building just south of the entrance to the slums. Hire him for 500 G and lose battles to see his scenes. The scenes focus on Hypnosis.
Lust < 100 - Kissing, Hypnosis
Lust < 200 - Sex, Hypnosis
Lust < 300 - Anal, Hypnosis
Lust < 400 - Sex, Mind Rewriting Complete
Lust < 500 - Sex in Bondage Costume
Lust > 500 - Scene not completely written and excluded due to errors
chose the 2nd to hardest dificulty for it 
